1. Field of the Invention
This application is a division of U.S. application Ser. No. 13/305,038, filed Nov. 28, 2011, and claims priority to Japanese Patent Application No. 2010-281102, filed on Dec. 17, 2010. The prior applications, including the specifications, drawings and abstracts are incorporated herein by reference in their entirety.
2. Description of Related Art
There has conventionally been known an optical measuring device including a power turret which can turn to switch a plurality of tube lenses each having a different magnification so as to select one of them, whereby magnification can easily be changed. With this configuration, the optical measuring device can be used for a visual observation of various measurement objects (workpieces) (see Japanese Patent No. 3363703, for example).
In a conventional optical measuring device 7, as illustrated in FIG. 7 for example, white light emitted from a white light source 710 passes through an objective lens 740 through a mirror 720 and a beam splitter 730 so that a workpiece W is irradiated with the white light. The white light with which the workpiece W is irradiated is reflected on a surface of the workpiece W, passes through one (a tube lens 750A in the figure) of a plurality of tube lenses 750 (750A, 750B, 750C), which is selectively switched by a power turret 760, via the objective lens 740 and the beam splitter 730, and enters a charge coupled device (CCD) camera 770. The conventional optical measuring device 7 observes an image of the workpiece W with the above-mentioned configuration.
Recently, there has been increased a demand for various observations and measurements, such as an observation of a wiring covered with a silicon or film, and an observation of a wiring covered by a resin film such as a solder resist formed on an integrated circuit (IC) wafer. However, the optical measuring device described above has a problem of having difficulty in observing the wiring, because the irradiated light is reflected on the surface of the workpiece W (i.e., is reflected before it reaches the wiring).
In order to solve the above-mentioned problem, there has been known a device which can perform a special observation such as a near-infrared observation and fluorescent observation, for example.
The near-infrared observation is an observation to be performed through a substance, through which near infrared light transmits, by utilizing a property of the near infrared light. Such property includes a property of having a longer wavelength than that of a visible light, a property of being invisible to naked eyes, and a property of passing through a thin material such as silicon and a film, and a skin tissue, differently from the visible light.
Examples of main usages of the near-infrared observation include an inspection of a circuit board using a thin material such as silicon and a film, and a vein authentication to be utilized for security.
As illustrated in FIG. 8, a conventional optical measuring device 8 for a near-infrared observation employs a special light source 810 which emits only near infrared light, such as a near-infrared light-emitting diode (LED) light source, and allows the near infrared light emitted from the special light source 810 to pass through an objective lens 840 via a mirror 820 and a beam splitter 830, so that the workpiece W is irradiated with the near infrared light. The near infrared light with which the workpiece W is irradiated passes through a surface of the workpiece W and is reflected on a not-illustrated wiring, passes through a tube lens 850 via the objective lens 840 and the beam splitter 830, and enters a CCD camera 860. The optical measuring device 8 for the near-infrared observation observes an image of the wiring inside the workpiece W with the above-mentioned configuration.
Meanwhile, the fluorescent observation is to irradiate a workpiece with excitation light corresponding to the workpiece, and to observe fluorescence emitted from the workpiece. Specifically, the fluorescent observation is to observe the wiring inside the workpiece by utilizing a phenomenon in which, after the light (excitation light) with which the workpiece is irradiated is absorbed by a pigment molecule of a fluorescent material formed on the surface of the workpiece, the fluorescent material emits light (fluorescence) according to a thickness of the fluorescent material. Since the thickness of the fluorescent material covering the wiring varies according to a structure of the wiring, the structure of the wiring can be found by observing an intensity of the fluorescence emitted from the fluorescent material. Here, the fluorescent material means a material which emits fluorescence, and includes a wide variety of materials. Thus, the excitation light corresponding to each fluorescent material and the wavelength of the fluorescence emitted from each fluorescent material are varied.
Examples of main usages of the fluorescent observation include an inspection of an IC wafer using a solder resist, and an observation of a biological tissue or cell stained with a fluorescent pigment.
As illustrated in FIG. 9, a conventional optical measuring device 9 for a fluorescent observation employs a special light source 910 which emits only excitation light, and provides an excitation filter 920, through which only excitation light having a wavelength corresponding to a workpiece W transmits, on an optical axis of the excitation light emitted from the special light source 910. With this configuration, the excitation light corresponding to the workpiece W is obtained, and the obtained excitation light transmits through an objective lens 950 via a mirror 930 and a dichroic mirror 940, so that the workpiece W is irradiated with the excitation light. Then, the fluorescence according to the thickness of the fluorescent material formed on the workpiece W is emitted from the workpiece W irradiated with the excitation light, and the excitation light is reflected on the workpiece W. The fluorescence and the excitation light from the workpiece W pass through a fluorescence filter 970, through which only fluorescence transmits, via the objective lens 950 and the dichroic mirror 940. The fluorescence passing through the fluorescence filter 970 passes through a tube lens 960 to enter a CCD camera 980. The conventional optical measuring device 9 for the fluorescent observation observes an image of the wiring inside the workpiece W with the above-mentioned configuration.
However, in the case of the configuration where the workpiece is irradiated with only the near infrared light, such as the above-mentioned optical measuring device for the near-infrared observation, the ordinary visual observation requiring irradiation of the workpiece W with the white light cannot be performed.
Similarly, in the case of the configuration where the workpiece is irradiated with only the excitation light corresponding to the workpiece, such as the above-mentioned optical measuring device for the fluorescent observation, the ordinary visual observation requiring irradiation of the workpiece W with the white light cannot be performed.